The human body includes long, short, flat, irregular and sesamoid bone. A long bone is characterized by a midshaft. The midshaft of a long bone is typically classified as the diaphysis. The end of such a bone is typically classified as the epiphysis. Bone that is transitional between the midshaft and the end is typically classified as the metaphysis.
Multi-segment fractures, of either the midshaft or end-bone, require alignment and stability in a manner that generates adequate fixation in multiple directions.
However, midshaft fractures and end-bone fractures are fundamentally different. The loading conditions, fracture patterns, alignment needed, and compression force to promote healing are different. Midshaft fractures have ample bone material on either side of the fracture in which anchors may be driven. End-bone fractures, especially on the articular surface may have thin cortical bone, soft cancellous bone, and minimal anchoring locations.
Midshaft fractures tend to be loaded primarily in bending and torsion. End-bone fractures tend to be loaded in complex and multi-directional stress patterns. Midshaft repair approaches, therefore, may not be appropriate for repair of end-bone fractures.
There are two primary categories for surgical fixation of a long bone fracture: (1) a device that is within the skin (internal fixation); and (2) a device that extends out of the skin (external fixation). There are two common types of internal fixation approaches for long bone surgery (a) a plate that is screwed to the outside of the bone; or (b) a rod that goes down the center of the bone.
Intramedullary rods, nails or implants, are more effective than plates and screws at minimizing soft-tissue trauma and complications. Moreover, appropriate sizing of an implant helps realignment and healing of the fracture. Proper sizing of an implant may ensure proper matching of the implant device to a patient's anatomy.
An implant deployed in an intramedullary cavity of a bone may be expandable. An expandable implant may provide proper anatomic alignment and allow appropriate sizing of the implant. However, bone fractures require alignment and stability in a manner that generates adequate fixation in multiple directions.
It would be desirable, therefore, to provide apparatus and methods for securing an implant deployed inside a bone.